Problem with Derivative x(t).VI

[jamiva]

The "Derivative x(t).VI" works when I select any method but "4th Order Central" using the default Inital and Final Conditions. The 4th Order produces an:

error -2006   "Analysis:  The number of samples must be >= 2."

The number of samples is 1000. The VI also produces the same error if I provide a data array to the Initial and Final Condition rather than using the default values. Am I doing something wrong? Is it a bug?

[jamiva]

I'm using LabVIEW 2014 Version 14.0.f1 (32-bit)

[GerdW]

Hi jarniva,

please read the help for the derivative function. It mentions some boundary conditions for the "4th order" calculation you need to supply!

[jamiva]

I did read the help file. It says that the initial and final conditions minimize the error at the boundaries. I assumed that the default conditions woud work the same for both the 2nd order and 4th order methods. 2nd order works perfectly. I tried wiring a constant array for the boundary conditions and got the same error. What is different between the two methods?

[GerdW]

Hi jamiva,

to quote the LabVIEW help for Derivative:

Initial Condition: If method is 4th Order Central, the VI uses the first two elements in Initial Condition to calculate the derivative. The default is [0].
Final Condition: If method is 4th Order Central, the VI uses the first two elements in Final Condition to calculate the derivative. The default is [0].

Again: Did you read the help for that function? Did you read all of the help? Do you understand what it says?